The present invention relates to apparatus for the preparation of lenses for eyeglasses prior to the edge shaping of the lenses, and more particularly to a device for determining the setting of a lens edger device.
The manufacturers of spectacle frames also provide lens patterns having a peripheral configuration corresponding to the peripheral configuration of the lens to be mounted in the spectacle frame. However, these lens patterns are not necessarily of the proper peripheral dimension to fit the lens openings of the spectacle frame. Lens patterns are typically used in conjunction with a lens edger device as a template to guide the lens edger device for forming a lens which is of the proper peripheral configuration to fit the lens opening of spectacle frames. The lens edger must be adjusted or set in order to form a lens which is of the proper peripheral size to fit the frame lens opening. Thus, the peripheral size of the lens opening of the spectacle frame must be determined in relationship to the lens pattern so that the lens edge device can be set to make a lens of the proper peripheral size and configuration.
A number of devices have been proposed for accomplishing this task. One example of a device for indicating the set size for a lens edger device required to edge grind the lens to fit the lens opening of a spectacle frame is shown in U.S. Pat. No. 3,457,652 issued on July 29, 1969 to Robert L. Moffett. The device includes two parallel slides mounted on a base, the top slide having a lens pattern abutment plate at one end and an index mark. The bottom slide has a scale along one edge and a spectacle lens opening engagement pin attached thereto. The base has a lens pattern abutment adjacent the end of the top slide having the lens pattern abutment, and a spectacle lens opening engagement pin in alignment with a lens opening engagement pin on the bottom slide. A lens pattern is positioned adjacent to the top slide between the lens pattern abutment on the top slide and lens pattern abutment on the base and the top slide is moved toward the lens pattern until both lens pattern abutments are in contact with opposite sides of the lens pattern. A spectacle frame is positioned at one end of the bottom slide with the lens opening abutment pins in diametrically opposed engagement with a lens opening of the spectacle frame. The index on the top slide then cooperates with the scale on the bottom slide to indicate the set size reading of the bevel edger required to produce a lens to fit the spectacle lens opening.
The above described device cannot be used to determine the lens edger device setting required for making lenses for rimless spectacles. In addition, the above described device has no provision for checking the accuracy of a lens pattern before it is used to determine the setting of the lens edger device.
An example of an instrument determining the setting of a lens edger device to produce a lens is disclosed in our U.S. Pat. No. 4,707,929 issued on Nov. 24, 1987. While this instrument works very well, some difficulty has been experienced in use in gauging the longest transverse dimension of the lens pattern and the spectacle frames lens opening because in many instances this longest transverse dimension is not on the horizontal axis of the lens pattern or the spectacle frame lens opening.